1. Field of the Invention
The present invention relates to farm implements, and, more particularly, to systems and methods for maintaining such implements level relative to the soil.
2. Description of the Related Art
In the continuing quest for providing greater efficiency in the operation of farm implements, machines have been constructed to have ever increasing lateral spans relative to a tractor or central unit propelling the unit over a field. When the span increases to realize greater efficiency and speed, the criteria of having a uniform and level tool contact with the soil becomes extremely critical. Equipment with significant lateral spans have many different joints and are usually articulated to enable transport to and between fields.
An area of special importance to level positioning of farm implements is found in the tillage field. The desirable outcome is a uniform physical depth of the tillage and a uniform entry of the disk blades or harrows into the soil. The need to have a level positioning of the implement is made more challenging with the use of hydraulic actuators which control the depth of penetration of the disk blades or other tools. In current practice, hydraulic actuators are connected in series and it is possible through normal operation for hydraulic fluid leakage to make the actuators out of sync with one another. In addition, field conditions, such as wheel loading and other variables, require an adjustment to the synchronization of the different sections of the tillage implement, thereby requiring the operator to dismount from a tractor and make manual adjustments.
It is current practice to partially counter this occurrence by fully elevating the implement to the point where bypass lands in the actuators allow full flow of hydraulic fluid to pass through the actuators and again synchronize the multiple units. However, this adds an additional step to the operation, particularly in the field, thereby decreasing the efficiency and speed with which the particular task is accomplished.
It has been proposed in co-pending application entitled “Remote Leveling of Tillage Implements Using Three-Way Valves”, of common assignment with the present invention to automatically adjust the hydraulic actuators in a system for leveling tillage implements by using three-way valves to enable a single hydraulic control for individual adjustment and to connect the actuators in series for common movement during field operation. This system provides the benefits of individual actuator adjustment while enabling a minimum length to hydraulic lines extending from a hydraulic control unit to the individual actuators. With such a system however, it is possible to entrain air in the additional connections between the three-way valves so as to take away from the objective that adjustment and operation takes place without any air in the system.
What is needed in the art therefore, is an effective apparatus and method for air removal in agricultural implements of the above type.